The Doctor: Dying defines us. Snow isn't snow til it falls.
Ruby: Snows.
The Doctor: It all melts away in the end, but something stays. Maybe the best part.

Do you get it? Do you get, get, get it? You declared war on an empty planet. There are no Kastorians. They're not in the mud. They're not in the fog. There's just an algorithm maintaining an acceptable casualty rate in the face of nothing at all.

Doctor

Doctor: It's just the adrenalin rush. I need to calm down. Slide... slide...
[The Doctor begins glowing]
Ruby: What's happening?
Doctor: I'm happening. It's me. I'm the explosion.

Doctor: This is Ruby and I'm the Doctor
Splice: That's not a name.
Doctor: And I'm not really a doctor. You're good. Most people don't even notice that.

It's vacuum drones, that's all, Hoovering up the smoke so no one can choke to death before they can be safely shot.

Doctor

Ruby: Why does a landmine have lights on it?
Doctor: Capitalism.
Ruby: Excuse me?
Doctor: Flashy lights play well in a showroom. Modern warfare. Death by salesmen.

Doctor: Everything's fine.
Ruby: Who said it wasn't?

Vader: Let me smell so I can see if your breath is minty fresh. Liar! You didn't brush your teeth.
Splice: How can you tell what my breath smells like over comm?
Vader: Dad skills.

More fog. Maybe the Kastorians are made of fog. That's why we never see them.

Carson

Doctor Who Season 1 Episode 3 Quotes

Vader: Let me smell so I can see if your breath is minty fresh. Liar! You didn't brush your teeth.
Splice: How can you tell what my breath smells like over comm?
Vader: Dad skills.

More fog. Maybe the Kastorians are made of fog. That's why we never see them.

Carson